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Petroleum Science 2008年第3期5卷 230-237页

作者： Xu Zhangyou Zhang Xiaoyu Wu Shenghe Zhao Yan School of Resources and Information Technology China University of Petroleum Beijing 102249 China State Key Laboratory of Petroleum Resources and Prospecting China University of Petroleum Beijing 102249 China

The genesis of a reservoir is a result of the combined action of deposition, diagenesis, tectonic reworking, and interaction of rock and fluid and the evolutionary environment. We discuss the genetic and evolution mechanism of a low-permeability reservoir bed of the Xujiahe Formation in the western Sichuan Depression on the basis of the study of diagenesis, diagenetic reservoir facies and the diagenetic evolution sequence. The research indicated that this reservoir bed can be divided into five types of diagenetic reservoir facies, namely strong dissolution, chlorite-lined intergranular pores, compaction and pressure solution, carbonate cementation and secondary quartz increase. There are, however, just two diagenetic reservoir facies which provide low-permeability reservoir beds, namely strong dissolution and chlorite-lined intergranular pores. We also analyzed their diagenetic evolution sequences and the origin of the low-permeability reservoir bed. Besides, it was also indicated that the composition and structure of sandstones, types of sedimentary microfacies, diagenesis history as well as the tectonic reworking in later periods are the main factors controlling the formation of the low-permeability reservoir bed. The above- mentioned factors establish the foundation for the forecasting the distribution of high quality reservoir beds.

关键词： low-permeability reservoir diagenetic reservoir facies Xujiahe Formation upper Triassic Xinchang gas field western Sichuan Depression

Fractal model of spontaneous imbibition in low-permeability reservoirs coupled with heterogeneity of pore seepage channels and threshold pressure

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Petroleum Science 2024年第2期21卷 1002-1017页

作者： Ming-Sheng Zuo Hao Chen Xi-Liang Liu Hai-Peng Liu Yi Wu Xin-Yu Qi a National Key Laboratory of Petroleum Resources and Engineering China University of Petroleum(Beijing)Beijing102249China b College of Safety and Ocean Engineering China University of Petroleum(Beijing)Beijing102249China

Spontaneous imbibition(SI)is an important mechanism for enhancing oil recovery in low-permeability reservoirs.Due to the strong heterogeneity,and the non-Darcy flow,the construction of SI model for lowpermeability reservoirs is extremely challenging.Commonly,traditional SI models based on single or averaged capillary tortuosity ignore the influence of heterogeneity of pore seepage channels and the threshold pressure(TP)on imbibition.Therefore,in this work,based on capillary model and fractal theory,a mathematical model of characterizing SI considering heterogeneity of pore seepage channels is established.On this basis,the threshold pressure was introduced to determine the pore radius at which the wetted phase can displace oil.The proposed new SI model was verified by imbibition experimental data.The study shows that for weakly heterogeneous cores with permeability of 0-1 m D,the traditional SI model can characterize the imbibition process relatively accurately,and the new imbibition model can increase the coefficient of determination by 1.05 times.However,traditional model has serious deviations in predicting the imbibition recovery for cores with permeability of 10-50 m D.The new SI model coupling with heterogeneity of pore seepage channels and threshold pressure effectively solves this problem,and the determination coefficient is increased from 0.344 to 0.922,which is increased by2.68 times.For low-permeability reservoirs,the production of the oil in transitional pores(0.01-0.1μm)and mesopores(0.1-1μm)significantly affects the imbibition recovery,as the research shows that when the heterogeneity of pore seepage channels is ignored,the oil recovery in transitional pores and mesopores decreases by 7.54%and 4.26%,respectively.Sensitivity analysis shows that increasing interfacial tension,decreasing contact angle,oil-water viscosity ratio and threshold pressure will increase imbibition recovery.In addition,there are critical values for the influence of these factors on the imbibition recovery,which provides theoret

关键词： Spontaneous imbibition low-permeability reservoir Fractal model Threshold pressure Capillary tube

Characteristics and mechanisms of supercritical CO_(2) flooding under different factors in low-permeability reservoirs

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Petroleum Science 2022年第3期19卷 1174-1184页

作者： Zheng Chen Yu-Liang Su Lei Li Fan-Kun Meng Xiao-Mei Zhou School of Petroleum Engineering China University of Petroleum(East China)Qingdao266580ShandongPR China Key Laboratory of Unconventional Oil&Gas Development(China University of Petroleum(East China)) Ministry of EducationQingdao266580ShandongPR China School of Petroleum Engineering Yangtze UniversityWuhan430100HubeiPR China

In recent years,supercritical CO_(2)flooding has become an effective method for developing lowpermeability reservoirs.In supercritical CO_(2)flooding different factors influence the mechanism of its displacement process for oil recovery.Asynchronous injection-production modes can use supercritical CO_(2)to enhance oil recovery but may also worsen the injection capacity.Cores with high permeability have higher oil recovery rates and better injection capacity,however,gas channeling occurs.Supercritical CO_(2)flooding has a higher oil recovery at high pressure levels,which delays the occurrence of gas channeling.Conversely,gas injection has lower displacement efficiency but better injection capacity at the high water cut stage.This study analyzes the displacement characteristics of supercritical CO_(2)flooding with a series of experiments under different injection and production parameters.Experimental results show that the gas breakthrough stage has the fastest oil production and the supercritical CO_(2)injection capacity variation tendency is closely related to the gas-oil ratio.Further experiments show that higher injection rates represent significant ultimate oil recovery and injection index,providing a good reference for developing low-permeability reservoirs.

关键词： low-permeability reservoir Supercritical CO_(2)flooding Influence mechanism Enhanced oil recovery Injection capacity

permeability and heterogeneity adaptability of surfactant-alternating-gas foam for recovering oil from low-permeability reservoirs

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Petroleum Science 2022年第3期19卷 1185-1197页

作者： Ming-Chen Ding Qiang Li Yu-Jing Yuan Ye-Fei Wang Ning Zhao Yu-Gui Han School of Petroleum Engineering China University of Petroleum(East China)Qingdao266580ShandongP.R.China Key Laboratory of Unconventional Oil&Gas Development(China University of Petroleum(East China)) Ministry of EducationQingdao266580ShandongP.R.China Research Institute of Petroleum Engineering Technology Shengli Oilfield CompanyDongying257000ShandongP.R.China Bohai Oilfield Research Institute Tianjin Branch of CNOOC Ltd.Tianjin300450P.R.China

As the traditional polymer stabilizer is eliminated to improve the injectability of foam in lowpermeability reservoirs,the stability,plugging capacity,conformance control and oil recovery performance of the surfactant-alternating-gas(SAG)foam become significantly important for determining its adaptability to permeability and heterogeneity,which were focused and experimentally researched in this paper.Results show that the SAG bubbles are highly stable in micron-sized channels and porous media(than in the conventional unconstrained graduated cylinder),making it possible to use in enhanced oil recovery(EOR).Such bubbles formed in porous media could be passively adjusted to match their diameter with the size of the pore.This endows the SAG foam with underlying excellent injectability and deep migration capacity.permeability adaptability results indicate a reduced plugging capacity,but,increased incremental oil recovery by the SAG foam with decreased permeability.This makes it a good candidate for EOR over a wide range of permeability,however,parallel core floods demonstrate that there is a limiting heterogeneity for SAG application,which is determined to be a permeability contrast of 12.0(for a reservoir containing oil of 9.9 m Pa s).Beyond this limit,the foam would become ineffective.

关键词： SAG foam EOR low-permeability reservoir permeability Heterogeneity

Importance of conformance control in reinforcing synergy of CO_(2) EOR and sequestration

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Petroleum Science 2022年第6期19卷 3088-3106页

作者： Yang Zhao Zhen-Hua Rui Zheng Zhang Si-Wei Chen Ren-Feng Yang Kai Du Birol Dindoruk Tao Yang Erling H.Stenby Malcolm A.Wilson State Key Laboratory of Petroleum Resources and Prospecting China University of Petroleum(Beijing)Beijing 102249China College of Petroleum Engineering China University of Petroleum(Beijing)Beijing 102249China College of Carbon Neutrality Future Technology China University of Petroleum(Beijing)Beijing 102249China College of Petroleum China University of Petroleum(Beijing)at KaramayKaramayXinjiang 83400China CNOOC Research Institute Co. Ltd.Beijing 100029China University of Houston USA Equinor Ovre StokkaveiStavangerNorway Technical University of Denmark Denmark University of Regina Canada

Injecting CO2into hydrocarbon reservoirs can enhance the recovery of hydrocarbon resources,and simultaneously,CO2can be stored in the rese rvoirs,reducing considerable amount of carbon emissions in the atmosphere.However,injected CO_(2)tends to go through fractures,high-permeability channels and streaks present in reservoirs,resulting in inefficient hydrocarbon recovery coupled with low CO_(2)storage performance.Conformance treatments with CO_(2)-resistant crosslinked polymer gels were performed in this study to mitigate the CO_(2)channeling issue and promote the synergy between enhanced oil recovery(EOR) and subsurface sequestration of CO_(2).Based on a typical low-permeability CO_(2)-flooding reservoir in China,studies were performed to investigate the EOR and CO_(2)storage performance with and without conformance treatment.The effect of permeability contrast between the channels and rese rvoir matrices,treatment size,and plugging strength on the efficiency of oil recovery and CO_(2)storage was systematically investigated.The results indicated that after conformance treatments,the CO_(2)channeling problem was mitigated during CO_(2)flooding and storage.The injected CO_(2)was more effectively utilized to recover the hydrocarbons,and entered wider spectrum of pore spaces.Consequently,more CO_(2)was trapped underground.Pronounced factors on the synergy of EOR and CO_(2)storage were figured out.Compared with the treatment size,the CO_(2)storage efficiency was more sensitive to the plugging strength of the conformance treatment materials.This observation was important for conformance treatment design in CCUS-EOR projects.According to this study,the materials should reduce the channel permeability to make the channel/matrix permeability ratio below 30.The results demonstrate the importance of conformance treatment in maximizing the performance of CCUS-EOR process to achieve both oil recovery improvement and efficient carbon storage.This study provides guidelines for successful field applications of CO_(2)transport co

关键词： Enhanced oil recovery(EOR) CO_(2)geological sequestration Conformance control Gel treatment CCUS low-permeability reservoir

SENSITIVITY COEFFICIENTS OF SINGLE-PHASE Flow IN low-permeability HETEROGENEOUS reservoirS

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Applied Mathematics and Mechanics(English Edition) 2002年第6期23卷 712-720页

作者：程时清张盛宗黄延章朱维耀 Faculty of Petroleum and Nature Gas Petroleum University in Beijing Changping Beijing 102249 P R China Institute of Porous Flow and Fluid Mechanics Academia Sinica Langfang Hebei 065007 P R China

Theoretical equations for computing sensitivity coefficients of wellbore pressures to estimate the reservoir parameters in low-permeability reservoirs conditioning to non-Darcy flow data at low velocity were obtained. It is shown by a lot of numerical calculations that the wellbore pressures are much more sensitive to permeability very near the well than to permeability a few gridblocks away from the well. When an initial pressure gradient existent sensitivity coefficients in the region are closer to the active well than to the observation well. Sensitivity coefficients of observation well at the line between the active well and the observation well are influenced greatly by the initial pressure gradient.

关键词： non-Darcy flow through porous media permeability porosity sensitivity coefficient inverse problem low-permeability reservoir

Simplified graphical correlation for determining flow rate in tight gas wells in the Sulige gas field

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Petroleum Science 2008年第3期5卷 258-262页

作者： Xiao Wei Wu Xiaodong Liu Xiaojuan Laboratory of Petroleum Engineering Ministry of Education China University of Petroleum Beijing 102249 China Xi＇an Shiyou University Xi＇an Shaanxi 710065 China

The Sulige tight gas reservoir is characterized by low-pressure, low-permeability and lowabundance. During production, gas flow rate and reservoir pressure decrease sharply; and in the shut- in period, reservoir pressure builds up slowly. Many conventional methods, such as the indicative curve method, systematic analysis method and numerical simulation, are not applicable to determining an appropriate gas flow rate. Static data and dynamic performance show permeability capacity, kh is the most sensitive factor influencing well productivity, so criteria based on kh were proposed to classify vertical wells. All gas wells were classified into 4 groups. A multi-objective fuzzy optimization method, in which dimensionless gas flow rate, period of stable production, and recovery at the end of the stable production period were selected as optimizing objectives, was established to determine the reasonable range of gas flow rate. In this method, membership functions of above-mentioned optimizing factors and their weights were given. Moreover, to simplify calculation and facilitate field use, a simplified graphical illustration （or correlation） was given for the four classes of wells. Case study illustrates the applicability of the proposed method and graphical correlation, and an increase in cumulative gas production up to 37% is achieved and the well can produce at a constant flow rate for a long time.

关键词： low-permeability reservoir sand thickness fuzzy optimization method gas flow rate

A Comprehensive Evaluation Method for low-permeability reservoirs

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Petroleum Science 2005年第4期2卷 9-13页

作者： Zeng Lianbo Wang Zhengguo Zhang Guibin Key Laboratory for Hydrocarbon Accumulation of Ministry of Education China University of Petroleum Beijing 102249 China Faculty of Geoscience China University of Petroleum Beijing 102249 China

According to the geological characteristics and their influential factors of the low-permeability reservoirs, a comprehensive method for evaluation of low-permeability reservoirs is put forward. The method takes a matrix system as the basis, a fracture system as the focus and a stress field system as the restricted factor. It can objectively reflect not only the storage capability and seepage capability of low-permeability reservoirs, but also the effect on development as well. At the same time, it can predict the seepage characteristics at different development stages and provide a reasonable geological basis for the development of low-permeability reservoirs.

关键词： Matrix system fracture system stress field system low-permeability reservoir comprehensive evaluation